Porsche 991/911 Turbo Porsche 996/997.2/991 Recirculating Valves - FORGE MOTORSPORT FMDV008P2

The Forge Motorsport FMDV008P2 is an upgraded turbo diverter/recirculation valve (DV) kit designed for twin-turbo Porsche applications. 

It is essentially an upgraded pressure-control component between the turbocharger system and intake tract—not a blow-off valve designed to vent boost to atmosphere.

Forge specifies the kit for Porsche 996 Turbo, 997.2 Turbo and 991 Turbo, as well as several other turbocharged Porsche applications. 

What does the valve actually do?

When the throttle closes while the turbo is producing boost, the compressed air suddenly has nowhere to go.

The recirculation valve opens:

Turbo → compressed air → diverter valve opens → air recirculated back into intake

This prevents the pressure wave from being forced back toward the compressor wheel.

When the throttle opens again:

Valve closes → boost is retained → turbo continues building pressure

So the DV is essentially a pressure-management device for the turbocharger system.

Why FMDV008P2 is different from OEM

Forge replaces the conventional valve design with a serviceable piston-type construction. The valve uses a 25 mm port and is designed for faster actuation and greater flow than the OEM-style valve. 

The important engineering differences are:

Feature	OEM-style DV	Forge FMDV008P2
Valve mechanism	Factory diaphragm/design	Piston
Construction	OEM specification	Upgraded metal/serviceable design
Serviceability	Generally replacement-oriented	Rebuildable/serviceable
Spring selection	Fixed factory calibration	Uprated spring options
Port	—	25 mm
Kit quantity	—	2 valves
Response	OEM calibration	Designed for faster response
Boost behaviour	Factory	Better suited to modified/high-boost systems

The kit contains two FMDV008 valves, two yellow springs and two blue springs, because the relevant Porsche applications use a pair of recirculation valves. 

The clever part: spring selection

The supplied springs allow the valve to be calibrated for the engine’s operating conditions.

This matters because a DV shouldn’t simply be “as stiff as possible.”

It needs to:

Open quickly when required → control compressor pressure → close positively → remain sealed under boost.

Too weak and the valve can potentially open when it shouldn’t. Too aggressive and the valve may not react as intended to the control signal.

Forge specifically provides yellow and blue uprated springs for adjustment. 

**Why this matters more on a modified 911 Turbo

For a relatively stock car, the OEM system can already perform its job adequately.

But once you increase:

• turbocharger flow
• boost pressure
• ECU calibration
• intercooler capacity
• intake flow
• throttle response
• turbocharger efficiency

…the DV becomes part of the overall boost-control system.

A leaking or slow DV can cause:

Boost pressure → valve leakage → compressor efficiency loss → slower boost recovery → inconsistent throttle response

An upgraded piston DV aims to keep that system tightly controlled.

Important distinction: it doesn’t create horsepower by itself

This is the key point.

FMDV008P2 is not a power-adder in the same sense as a turbocharger, intercooler or ECU tune.

Its primary job is to control and retain the boost that the turbo system is already producing.

Therefore, the biggest benefit is generally:

boost control + response + reliability/serviceability

rather than a dramatic peak-horsepower increase.

Forge also recommends servicing the valves every 3 years or 20,000 miles, whichever comes first. 

The Porsche engineering picture

Think of the system as:

Turbocharger
↓
Compresses air
↓
Intercooler
↓
Throttle
↓
Engine

When throttle suddenly closes:

Throttle closes
↓
Boost pressure rises upstream
↓
DV opens
↓
Pressure is recirculated
↓
Compressor remains protected from the pressure event
↓
Throttle reopens
↓
DV closes rapidly
↓
Boost recovery

That’s why a good DV is particularly relevant to a twin-turbo Porsche 911 where rapid throttle transitions are part of the car’s performance character.

Bottom line: FMDV008P2 is best understood as a high-performance, serviceable twin recirculation-valve system for Porsche turbo engines. Its value is in better boost-pressure management, fast valve response, sealing and long-term serviceability, rather than simply adding horsepower. 

Porsche 991/911 Turbo Porsche 996/997.2/991 Recirculating Valves - FORGE MOTORSPORT FMDV008P2